New Anthropic flagship released 30 May 2026. Adds the dropdown entry as
the new default for fresh agents, maps "opus-4-8" -> "claude-opus-4-8" in
ResolveModelId, and bumps the "opus" alias from 4.7 to 4.8 so the family
shortcut tracks the latest release.
ARCHITECTURE.md updated to list opus-4-8 in both the field reference and the
model-resolution block.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
